Pressure actuated switch



March 18, 1958 B. H. CLASON 2,827,526

PRESSURE ACTUATED SWITCH Filed D60. 10, 1954 ATTORNEY United StatesPatent PRESSURE ACTUATED SWITCH Bertil H. Clason, Flint, Mich, assignorto General Motors Corporation, Detroit, Mich., a corporation of DelawareApplication December 10, 1954, Serial No. 474,385

2 Claims. (Cl. 200-83) This invention relates to pressure actuatedswitches and more particularly that type which utilizes a diaphragm foractuating bridging contacts to control an electrical circuit.

Switches of this type find numerous applications in control andindicating devices for fluid pressure systems. Such switches arecommonly used in automotive vehicles and must therefore be of ruggedconstruction, reliable in operation, and economical to manufacture. Incertain applications, it is required that the switch operate to completethe circuit, upon actuation in one sense, while in other applicationsthe switch must operate to interrupt the circuit, upon actuation in thesame sense. Thus, it is desirable that the operating function of theswitch may be changed from make to break by a simple operation withoutthe necessity of complex or special parts.

Accordingly, it is an object of this invention to provide a switchstructure adapted to selectively make or break an associated circuit inresponse to the same actuation.

It is another object of this invention to provide a change-functionswitch of simple rugged construction requiring few parts and permittingselection of operating function by a simple rearrangement.

It is a more specific object of this invention to provide an electricalswitch of the contact bridging type which utilizes the terminal posts asfixed contacts'and which operates to selectively close or open thecircuit in response to the same actuation.

These and other objects and the manner in which they are achieved willbecome apparent from the description which follows, taken with theaccompanying drawing in which:

Figure 1 is an elevational view in section of the switch.

Figure 2 is a fragmentary view showing a rearrangement of certain switchparts.

Figure 3 is a perspective view of the contact insulating member.

The inventive switch comprises a pair of laterally spaced terminal postsprovided with axially spaced contact elements and a bridging contactmember having a portion movable between the spaced contact elements. Aninsulating member is disposed between the spaced contact elements andmay be positioned on either side of the contact member to provide thedesired function of interruption or completion of the circuit uponactuation of the contact member in a given direction.

Referring now to the drawings, an exemplary embodiment is shown in whichthe switch is actuated in response to fluid pressure and is adapted tocontrol the electrical continuity of an associated circuit. The switchstructure comprises a metal shell 10, generally cylindrical in crosssection, which has a threaded nipple portion 11 adapted to be connectedto an associated fluid pressure system. The shell is provided with aradial shoulder portion 12 and an adjacent axial fiange 13. An annular2,821,526 Patented Mar. 18, 19 58 ice gasket 14 is seated againstshoulder 12 forming a fluid tight seal therewith.

A distendable diaphragm 15, which may be suitably constructed of metalsuch as stainless steel, is disposed within the shell 10 against gasket14. The diaphragm 15 and the shell 10 define a pressure chamber 16having a passage 17 through the nipple portion of shell 10 for theadmission of fluid pressure. Disposed adjacent one face of the diaphragm15 is a bearing plate 18 of insulating material in the form of anannular disk having an inwardly extending tongue portion 19. A gasket 20is fitted tightly against the bearing plate 18 and the flange 13 toprovide a fluid tight seal.

An insulating support member 21, which is is suitably a molded body of athermosetting phenolic plastic, is provided with an annular flange 22which is seated against gasket 20. The insulating support member 21 isformed with a hollow end portion or recess 23 to accommodate certainmembers of the switch will be described subsequently. The shell 10 has aradial flange 24 crimped over flange 22 of the insulating support memberto compress the gaskets 14 and 20 and to secure the parts together. Theshell 10 and insulating support member 21 form a two-part housing forthe entire switch structure.

A terminal member or post 26 extends axially through the insulatingsupport member 21 into the recess 23. The outer end 27 of terminal post26 is adapted to be connected to an electrical circuit while itsintermediate portion is formed with a knurled section 28 and undercutportions 29 to securely retain the post in the insulating supportmember. The inner end of the post 26 is provided with a lateral recessor notch 30 which is bounded by axially spaced contact elements or walls31 and 32. Similarly, terminal member or post 26' extends axiallythrough the insulating support member 21 into the recess 23 with itsouter end 27' adapted to be connected to an electrical circuit and withits intermediate portion formed with knurled section 28 and undercutportions 29'. The inner end of the post 26 is provided with a lateralrecess or notch 30' which is bounded by axially spaced contact elementsor walls 31' and 32'. The recesses 30 and 30' are disposed oppositelyand open inwardly or towards each other.

A contact member or cup 33 is disposed generally between the terminalposts 26 and 26 and is movable axially thereof to serve as an electricalbridge across the terminals, The contact member is provided with a baseor bearing portion 34 engaging the tongue portion 19 of bearing plate 18and an annular rim or projecting contact portion 36 which extendspartially into each of the recesses 30 and 30. Resilient means such ascoil spring 37 is interposed between the depressed portion 38 in contactcup 33 and the spacer ring 35 seated against adjustable set screw 39.The set screw is disposed in axial opening 40 and threadedly engages thewalls thereof to permit axial positioning of the screw and adjustment ofthe force exerted by the spring. This permits variation of the biasforce exerted on the diaphragm 15 for effecting calibration. Once thebias force has been established the set screw may be secured in positionby a suitable sealing compound 41 deposited within the opening 40.

An insulating member or plate 42 having a central opening 43 ispositioned coaxially of the contact cup 33.

The insulating plate 42 is provided with notches 44 and. 44' at oppositesides thereof which are interlocked with Thus, rim portion 36 may bedisplaced from engagement with contact elements 31 and 3 to control theelectrical continuity between the terminal posts 26 and 26'.

With the parts arranged as shown in Figure 1 in which insulating member42 is adjacent contact elements 32 and 32' of recesses 3i) and 30', theswitch functions to interrupt the circuit in response to increasingpressure. Upon the admission of a predetermined value of fluid pressurethe diaphragm exerts sufficient force against bearing member 18, contactmember 33 and spring 37 to displace the rim portion 36 from engagementwith the contact elements 31 and 31 on the terminal posts. Thisinterrupts the electrical circuit between the terminal 26 and theterminal 26. Upon further increase of fluid pressure, the rim portion 36is moved into engagement with the insulating plate 42. The insulatingplate prevents the electrical circuit from being completed between thecontact elements 32 and 32. In this condition the contact member 33 isfirmly seated against the insulating plate 42 which is supported by thete'rminal posts and an increase of pressure is ineffective to causefurther displacement. By reason of the bearing area afforded thediaphragm by the bearing portion of the contact member and the bearingplate, the diaphragm is protected from damage by excess pressures. Whenthe fiuid pressure is decreased below thepredetermine'd value; thecontact member 33 is moved under the influence of the spring 37 againstthe bearing plate and the diaphragm until the rim portion 36 of the cupengages walls 31 and 31. At this point the continuity of theelectrical'cir cuitis restored; a

By a simple rearrangement, as shown in Figure 2; the operating functionof the switch is changed by positioning the insulating plated/2 on theopposite side or rim portion 36 against contact elements 31 and 31.assembled relation the operation is similar to that described aboveexcept that the circuit is normally interrupted because the bias forceor" spring 37 urges the rim portion 36 into engagement with insulatingmember 42.

An increase of fluid pressure causes the diaphragm to displace the rimportion 36' into engagement with contact elements 32 and 32 to completethe circuit. The insulating member 42 prevents the circuit from beingcompleted upon a decrease of pressure when the contact cup 33 isreturned by the spring 37. i

It will now be apparent that the insulating member 42 may be positionedwith respect to contact cup 33 in accordance with the desired operatingfunction of the switch. In applications where the circuit betweenterminal posts 26 and 26 is to be interrupted in response to increasingpressure, the insulating member 42 is positioned adjacent contactelements 32 and 32 of recesses 30 and 36. Where the circuit is to becompleted in response to increasing pressure, the insulatingmember 42 ispositioned adjacent contactelements 31 and 31' of recesses 30 and 30'.Calibration to cause switch operation at a desiredvalue may be readilyaccomplished by adjustment of set screw 39. i

in this Although this invention has been described in detail withrespect to a particular embodiment, such embodiment is illustrative onlyand is not to be construed in a limiting sense. Numerous modificationsand variations within the spirit and scope of the invention will nowoccur to those skilled in the art. For a definition of the invention,reference is made to the appended claims.

I claim: 7

l. A pressure actuated switch comprising a casing and an axiallydistendable diaphragm defining a pressure chamber, means for admittingfluid pressure to said chamber against one side of said diaphragm, apair of spaced electrical terminal members supported by said casing onthe other side of said diaphragm said terminal members definingoppositely disposed notches and providing a pair of front and an axiallyspaced pair of back fixed contacts, a movable contact member having abearing por tion adjacent said diaphragm and a rim portion extendinginto said notches'whereby transverse motion of the contact'm'e'rnb'er islimited in one direction by said terminal members, an insulating plateinterposed between said rim portion and one pair of fixed contacts, saidinsulating plate defining oppositely disposed notches interlocked withsaid terminal members and having axially extending portions wherebytransverse motion of the contact member is limited in the otherdirection, and resilient means for urging said contact member towardsaid diaphragm whereby the electrical continuity between said terminalmembers is afiected by the position of the said diaphragm.

2. An electrical switch comprising a housing including an insulatingbody, a pair of terminals supported by said body, each of said terminalsbeing provided with a pair of axially spaced rigid contact elements, aninsulating member extending between both pairs of spaced contactelements, a bridging contact member having a'bearing portion and beingmovably disposed between both pairs of spaced contact elements, saidinsulating member being positionally interlocked with said terminals andsaid contact member and disposed on one side of the latter for retainingthe latter against lateral movement, said insulating member beingalternately disposable on the other side of said contact member andpositionally interlocked with said terminals and said contact member,resilient means normally urging said contact member toward engagementwith one of said contact elements of both terminal members, adistendaole diaphragm engaging said bearing portion for moving saidcontact member against said resilient means toward engagement with theother of said spaced contact elements of both contact elements wherebythe movement of said contact member and the distension of said diaphragmare limited by the spacing of said contact elements, and means supportedby the insulating body for adjusting theforce exerted by the resilientmeans.

References Cited in the file of this patent UNITED STATES PATENTS1,902,743 Whittingham Mar. 21, 1933 1,996,891 Van Valkenburg Apr. 9,1935 2,331,826 Davenport Oct. 12, 1943 2,430,428 Katc her Nov. 4, 19472,454,288 Michaelson 7 Nov. 23, 1948 2,466,111 Katcher et al Apr 5, 19492,468,768 Malick May 3, 1949 2,520,353 Del Campo et al. a Aug. 29, 19502,698,887 Shaw Ian. 4, 1955

